PostgreSQL
PostgreSQL, often simply Postgres, is an Object-Relational Database Management System (ORDBMS). It is released under an MIT-style license and is thus free and open source software. As with many other open source programs, PostgreSQL is not controlled by any single company, but has a global community of developers and companies to develop it.
See also http://www.enterprisedb.com/
See also http://www.enterprisedb.com/